How to get old variable value from PL/SQL for loop? - sql

Question

I am trying to get old value from variable in PL/SQL for loop.
For instance:
I have l_sequnce variable with increment of 10.
for x in (select name
from test_names
order by position)
loop
-- print l_sequnce variable
-- when name is already was in loop then write same value from l_sequence as for first one
end loop;
I hope I described the problem well :)

Answer 1

Use ORDER BY in the SELECT statement and then you only need to check if the value has changed between the previous and current values:
DECLARE
v_name TEST_NAMES.NAME%TYPE := NULL;
l_sequence PLS_INTEGER := 0;
BEGIN
FOR x IN (select name from test_names ORDER BY name)
LOOP
IF x.name <> v_name
OR (x.name IS NULL AND v_name IS NOT NULL)
OR (x.name IS NOT NULL AND v_name IS NULL)
OR l_sequence = 0
THEN
l_sequence := l_sequence + 10;
v_name := x.name;
END IF;
DBMS_OUTPUT.PUT_LINE(l_sequence || ': ' || x.name);
END LOOP;
END;
/
Or, don't use PL/SQL and do it all in an SQL statement using the DENSE_RANK analytic function:
SELECT name,
10 * DENSE_RANK() OVER (ORDER BY name) AS seq_value
FROM test_names
ORDER BY name; -- or whatever other column you want to order by.
If you want to do it entirely in PL/SQL and cannot use ORDER BY then use an associative array:
DECLARE
TYPE t_name_seq_map IS TABLE OF PLS_INTEGER INDEX BY VARCHAR2(30);
v_names t_name_seq_map;
l_sequence PLS_INTEGER := 0;
BEGIN
FOR x IN (SELECT name FROM test_names ORDER BY position)
LOOP
IF NOT v_names.EXISTS(x.name) THEN
l_sequence := l_sequence + 10;
v_names(x.name) := l_sequence;
END IF;
DBMS_OUTPUT.PUT_LINE(v_names(x.name) || ': ' || x.name);
END LOOP;
END;
/
or:
BEGIN
FOR x IN (
SELECT name,
DENSE_RANK() OVER (ORDER BY name) AS l_sequence
FROM test_names
ORDER BY position
)
LOOP
DBMS_OUTPUT.PUT_LINE(x.l_sequence || ': ' || x.name);
END LOOP;
END;
/